Remove fedora-31 testing

Fedora 32 and 33 are current. We can clean up this fedora 31 testing.
A followup change will add fedora-33 jobs.

Change-Id: I84357f9bffc104760fa673035f0d0bd095e9a892

.zuul.d/jobs.yaml

@@ -177,16 +177,6 @@
         # TODO: set when CentOS 8 Stream repos mirrored.
         # mirror: "http://{{ zuul_site_mirror_fqdn }}/centos"
 
-- job:
-    name: dib-nodepool-functional-openstack-fedora-31-src
-    description: |
-      Test building and booting a Fedora 31 image with Nodepool and OpenStack
-    parent: dib-nodepool-functional-src-base
-    vars:
-      nodepool_diskimage:
-        base_element: fedora-minimal
-        release: '31'
-
 - job:
     name: dib-nodepool-functional-openstack-fedora-32-src
     description: |

.zuul.d/project.yaml

@@ -17,7 +17,6 @@
         - dib-nodepool-functional-openstack-centos-7-src
         - dib-nodepool-functional-openstack-centos-8-src
         - dib-nodepool-functional-openstack-centos-8-stream-src
-        - dib-nodepool-functional-openstack-fedora-31-src
         - dib-nodepool-functional-openstack-fedora-32-src
         - dib-nodepool-functional-openstack-ubuntu-xenial-src
         - dib-nodepool-functional-openstack-ubuntu-bionic-src
@@ -49,7 +48,6 @@
         - dib-nodepool-functional-openstack-centos-7-src
         - dib-nodepool-functional-openstack-centos-8-src
         - dib-nodepool-functional-openstack-centos-8-stream-src
-        - dib-nodepool-functional-openstack-fedora-31-src
         - dib-nodepool-functional-openstack-fedora-32-src
         - dib-nodepool-functional-openstack-ubuntu-xenial-src
         - dib-nodepool-functional-openstack-ubuntu-bionic-src